In today's hand-held electronic devices such as modern smart phones, proximity sensors are widely used, e.g., for switching off a background illumination of an LCD screen of the device or for deactivating a capacitive element otherwise allowing the operation of a touch screen of the device. Such proximity sensors are typically located near an earpiece of the device and can recognize the appearance of a cheek or an ear of a user near the screen by detecting infrared (IR) light reflected from nearby objects. Upon detection of such reflected IR light, desired action can be initiated. The IR light is usually emitted by an LED which may be comprised in the proximity sensor.
Commercially available proximity sensors which have to be combined with a separate light emitter are, e.g., the Infrared Sensor Si1141 of Silicon Laboratories Inc, Texas, USA, the Light-to-Digital Converter with Proximity Sensing TSL2771 of Texas Advanced Optoelectronic Solutions Inc., Texas, USA, and the I2C Proximity Sensor with Ambient Light Sensor and Interrupt CM3623 of Capella Microsystems Inc., California, USA.
A commercially available proximity sensor comprising an IR LED and two photodiodes is, e.g., the SFH 7773 of OSRAM Opto Semiconductors.
From US 2009/159900 A1, a proximity sensor is known which comprises an IR transmission die and an IR receiver die as well as two lenses each arranged above one of the dies.
From US 2010/0327164 A1, a proximity sensor is known, during the manufacture of which light emitter dice and light detector dice are overmolded using transfer molding techniques so as to form lenses on these dice.
It can be problematic to achieve a safe proximity detection, in particular when an energy-saving operation has to be ensured. An furthermore, some proximity sensors are too large for certain applications.